In well-drilling operations, a rotor tong is used to grip and rotate lengths of pipe or rods which are connected together by threaded end sections. In the usual case, the tong is of the open-headed type, having a bifurcated frame with a central opening and an outwardly-open passageway which permits the tong to be positioned around a pipe joint without the necessity of lowering the tong over a length of the pipe.
When the tong is operated, pipe-gripping means are caused to revolve around the aforesaid central opening, these jaws causing the pipe or casing section to rotate. In the case of drill pipe or rod, the jaws are moved radially inwardly by a cam action to engage and clamp against the sides of the drill pipe which is relatively thick-walled. On the other hand, when a relatively thin-walled casing is being inserted into the well, the force exerted by radially-inwardly moving jaws will deform the tube wall. Accordingly, it has been common, when inserting casing into the well, to utilize jaws which rotate inwardly toward the casing about pivot points. Since the same type of clamping element cannot be used on both drill pipe and casing, it is desirable to provide interchangeable jaws on the same tong. In the past, however, so-called interchangeable tong systems required virtual complete disassembly and reassembly of the entire tong when changing from one type of jaw to the other.